Development of Empirical Correlation Between Shear Wave Velocity and Standard Penetration Resistance in Soils of Chennai City

Abstract eng:
During an earthquake, the ground motion characteristics of the site are significantly affected by the presence of soil deposits. The ground motion characteristics at the surface are evaluated by simplified site classification method or by carrying out rigorous site specific ground response analysis. In all these methods, the shear wave velocity (Vs) is the most important parameter which represents the stiffness of the soil layers and it is related to the amplification of the ground. The shear wave velocity profile is usually obtained by carrying out wave propagation tests in the field. But it is often not economically feasible to conduct these tests at all the sites. Therefore, a reliable empirical correlation between Vs and SPT-N would be a considerable advantage. This paper presents a development of reliable regression equation between Vs and SPT-N based on the shear wave velocity measurement carried out by Multi channel Analysis of Surface Wave (MASW) test at various sites in Chennai city. In Chennai city, the soil formation mainly consists of soft marine clay, stiff clay and loose sand with thickness varies from a few meters to 50 m. The Multichannel Analysis of Surface Wave (MASW) tests has been carried out at thirty sites distributed spatially for which SPT-N value profiles are available. Geometrics make 24 channel - seismic recorder with 4.5 Hz geophones were used to receive the wavefields. The acquired surface wave data were processed to develop shear wave velocity profile of the site. Based on the statistical assessments, an empirical correlation between Vs and SPT-N was developed. The regression equation developed in this study exhibits good prediction performance and it can be used for sites which predominantly consist of very soft to very stiff clay and very loose to dense sand.

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